ABSTRACT The Development Core will catalyze development of vanguard interventions designed to reduce HIV incidence in key populations (e.g., men who have sex with men (MSM) of color, youth, transgender individuals, African American women, prisoners), especially those who face substance use and mental health disorders. It will mobilize CHIPTS scientists and affiliates to develop novel, high-risk/high-payoff scientific advancements, to deliver cutting edge information on combination HIV prevention via networking events, and to mentor and train the next generation of HIV scientists. The Development Core is pivotal in promoting research focused on CHIPTS' themes to optimize the HIV care and prevention continua by addressing substance misuse and mental health. These themes focus core activities toward pushing scientific innovation, mentoring new leaders in bringing novel and high impact interventions to scale, guiding efforts domestically and globally to get to zero HIV transmissions. Its three specific aims are: (1) SCIENCE: To stimulate cutting edge HIV prevention and treatment science via pilot funding, peer review, and grant development activities that facilitate innovation, leadership, and impact on HIV prevention science for CHIPTS members, affiliates, and local and global partners; (2) NETWORKING: To establish new and nourish existing linkages for CHIPTS members and affiliates to lead CHIPTS' vision for the HIV prevention science agenda locally and globally. Emphasis is placed on building multidisciplinary teams required to effectively addressing mental health and substance use disorder comorbidities, and prevention and treatment continua outcomes. Emerging and established investigators will be networked with academic, medical, public health, and community-based partners; and (3) CAPACITY BUILDING: To provide scientific support and training focused on CHIPTS' key priorities of addressing substance use and mental health disorder comorbidities that contribute significantly to failures in the HIV prevention and care continua. The Development Core is led by Director Dallas Swendeman, PhD, Co-Director Roger Detels, MD, and Associate Director Maryann Koussa, MPH. The Development Core plays a central role in synergizing activities across Cores and with other centers, departments, and partner agencies. The Development Core is responsible for administering the pilot fund program, coordinating peer review for manuscripts and grant applications, organizing think tanks and conferences, developing capacity building resource for dissemination, and providing support to trainees in T32, Fogarty, R25, and doctoral training programs at UCLA and partner institutions.